Composition for flame cultivation



United States Patent 3,297,421 COMPOSITION FOR FLAME CULTIVATION JackRyer, East Brunswick, and Paul M. Kerschner, Trenton, N.J., assignors toCities Service Oil Company, Bartlesville, Okla, a corporation ofDelaware No Drawing. Filed Mar. 25, 1965, Ser. No. 442,804 13 Claims.(CI. 4452) The present invention relates to liquid petroleum hydrocarbonfuel compositions, and more particularly to liquified petroleum gascompositions. In another aspect, the invention relates to improvementsin the cultivation of crops by means of liquified petroleum gas flames.

Liquified petroleum gas, more commonly known as LPG, burns with anon-luminous flame, which is particularly diflicu-lt to see in brightdaylight. The nonluminosity of the LPG flame causes certain diflicultiesin some applications of LPG. ,One such application in which thenon-luminosity of the LPG flame poses problems is flame cultivation ofcrops. In flame cultivation procedures, an LPG flame is used to ,destroyor impair weed or like undesirable vegetation in or adjacent to a plantrow. In order to effectively burn the neighboring weeds without unduedamage to the desired crop, it is desirable that the person carrying outthe flame cultivation be able to see the total flame area or pattern.However, because of the non-luminosity of LPG flames in brightday-light, it is extremely diflicult to determine the flame front andwhether all of the burners are in operation. Consequently, some of thedesired crop may be damaged and/or some of the undesired neighboringgrowth may not be destroyed.

It is, therefore, one object of the present invention to provide acomposition of matter comprising liquified petroleum gas which uponburning yields a flame having a visible color.

It is a further obect of the invention to provide a liquified petroleumgas composition which may be used with advantage in the flamecultivation of crops.

It is still a further object of the invention to provide a moreeflicient flame cultivation process, whereby the cultivation flame canbe easily seen by the operator and, consequently the application of theflame may be adjusted to enable the most eflective destruction ofneighboring weeds and other undesirable vegetation, without undue damageto the crop.

Various other objects and advantages of the invention will appear fromthe following detailed description thereof, and the novel featuresthereof will be particularly pointed out in connection with the appendedclaims.

Briefly, the composition provided by the invention comprises LPG as themajor ingredient and having dissolved therein a readily vaporizablechromophoric material in an amount sufficient to impart a visible colorto a flame of LPG.

The LPG component of the compositions of the present invention is aliquified normally gaseous hydrocarbon having not more than four carbonatoms. Preferably, the LPG will be at least predominantly liquifiedpropane. Thus, a mixture of liquified propane and liquified butane inwhich the propane is present in the major amount, e.g. 80%, may be used.Minor quantities of unsaturated hydrocarbons such as propylene andbutylene may also be present.

The chromophoric materials useful in the practice of the presentinvention are compounds of elements which impart a visible color to theflame. Compounds boiling within range of --l C to +15 C. areparticularly advantageous. For instance, the compound of thechromophoric element may be arsenic fluoride, arsenous hydride,methylarsine, boron trifluoride, boron hydride (boro- "ice ethane),boron trimet-hyl tellurium (ii-hydride and hydrogen selenide. Accordingto a particularly preferred embodiment of the invention, the LPG ispredominantly liquified propane, e.g. and the compound of thechromophoric element dissolved therein has a boiling point of from about60 V. to about +5 C.

As previously noted, the amount of the compound of chromophoric elementin the LPG should be sufficient to impart a visible color to the flame.The actual quantity of the compound required for this purpose is, ofcourse, dependent upon the particular chromophoric element containedtherein, but generally is at least about 5 p.p.m. of element by weightof the LPG and preferably from about 10 p.p.m. to 10%, by weight, of theLPG. The color imparted to the flame as a result of adding the compoundof the chromophoric element to the LPG is not particularly important solong as it is readily visible. Hydrogen selenide and thearsenic-containing compounds noted above tend to impart a light bluecolor to the flame, while the telluriumand boron-containing compoundsimpart a green color.

A suitable amount of the readily vaporizable compound of thechromophoric element may be dissolved in the LPG and the resultantcomposition placed in a container under a suitable pressure (e.g. to 250p.s.i.). In use, the composition is propelled from the container to aburner wherein it is burned to produce a visible colored flame. Thedifference between the pressure in the container and atmosphericpressure causes LPG to readily vaporize as it is projected from thecontainer to the burner. Because the chromophoric compounds used in thepractice of the present invention have boiling points which arerelatively on the same order as LPG, they readily vaporize with the LPGand are projected with it to the burner. Thus, important features of theinvention are that the readily vaporizable, soluble, compounds ofchromophoric elements do not cause fouling or clogging of the valves ororfices of the container, and are not left behind in the container uponrelease of the LPG therefrom.

As mentioned hereinbefore, the compositions of the present invention areof particular use in flame methods for cultivating crops. Flamecultivation methods and apparatus are well-known in the art and,therefore, need not be described herein in great detail. Generally, incarrying out process of this type, a flame cultivation assemblycomprising burners and a container of LPG communicating therewith, iscarried behind a tractor traveling along and between the crop rows. Theburners are so positioned as to direct flames in a predetermined patterntoward the crop rows as well as toward the furrows, thereby eradicatingneighboring weed growth from the crop rows. By using the LPG compositionof the present invention as the fuel, the flames issuing from theburners may' be readily seen by the operator. Thus, the operator caneasily detect the flame pattern and whether all the burners are inoperation, thereby enabling him to make appropriate adjustments toinsure the most effective eradication of the weeds with the least damageto the crop.

The invention will now be further described with reference to thefollowing illustrative and non-limitative examples:

Example 1 Hydrogen selenide (B.P. -42 C.) is charged into a cylindercontaining liquified petroleum gas under a pressure of about 200 p.s.i.to provide a composition containing about 50 parts of selenium permillion parts of LPG by weight. The LPG component of the compositioncom- 0 prises about propane and a total of about 5% butane, butylene andpropylene, and has a boiling point of about -40 C. Upon being propelledfrom the cylinder, vaporized and ignited, the composition burn with avisible blue flame.

Example 2 Example 1 is repeated, except that tellurium hydride (B.P. C.)is used instead of hydrogen selenide. The resultant composition burnswith a visible green flame.

Example 3 Example 1 is repeated, except that methylarsine (B.P. 2 C.) isused instead of hydrogen selenide. The resultant composition burns witha blue flame.

Example 4 Example 1 is repeated, except that arsenic trifluoride (B.P.-53 C.) is charged to the cylinder instead of hydrogen selenide in anamount sufiicient to provide a composition containing about 5 parts ofarsenic per million parts of LPG by weight. The resultant compositionburns with a blue flame.

Example 5 Example 1 is repeated, except that arsenous hydride (B.P. -55C.) is charged to the cylinder instead of hydrogen selenide in an amountsufficient to provide a composition containing about 10,000 parts ofarsenic per million parts of LPG by weight. The resultant compositionburns with a blue flame.

Example 6 Example 1 is repeated except that boron trifluoride (B.P. C.)is charged to' the cylinder instead of hydrogen selenide in an amountsufficient to provide a composition containing about 10,000 parts ofboron per million parts of LPG by weight. The resultant compositionburns with a green flame.

Example 7 Example 8 Example 1 is repeated, except that boron trimethyl(B.P. C.) is charged to the cylinder instead of hydrogen selenide in anamount suflicient to provide a composition containing about 100 parts ofboron per million parts of LPG by weight. The resultant compositionburns with a green flame.

It will be understood that various changes in the details hereindescribed and illustrated in order to explain the nature of theinvention may be made by those skilled in the art within the principleand scope of the invention, as expressed in the appended claims.

Therefore, we claim:

1. a liquified petroleum gas composition consisting essentially ofliquified petroleum gas having not more than four carbon atoms as themajor ingredient and dissolved therein a readily vaporizable compound ofa chromophoric element in an amount suflicient to impart a visible colorto a flame of said liquified petroleum gas.

2. Composition as in claim 1 wherein said readily vaporizable compoundof a chromophoric element has a boiling point of from about 105 C. toabout 15 C.

3. Composition as in claim 1 wherein said readily vaporizable compoundis arsenic fluoride.

4. Composition as in claim 1 wherein said readily vaporizable compoundis arsenous hydride. I

5. Composition as in claim 1 wherein said readily vaporizable compoundis methylarsine.

6. Composition as in claim 1 wherein said readily vaporizable compoundis boron trifluoride.

7. Composition as in claim 1 wherein said readily vapor izable compoundis boron hydride.

8. Composition as in claim 1 wherein said readily vaporizab-le compoundis boron trimethyl.

9. Composition as in claim 1 wherein said readily vaporizablechromophoric material is tellurium dihydride.

10. Composition as in claim 1 wherein said readily vaporizable compoundis hydrogen selenide.

11. Composition as in claim 1 wherein said liquified petroleum gas is atleast predominantly liquified propane.

12. Composition as in claim 2 wherein said readily vaporizable compoundof a chromophoric element is' dissolved in said liquified petroleum gasin an amount of at least about 5 parts of element per million parts ofliquified petroleum gas, by Weight.

13. Composition as in claim 11 wherein said readily vaporlzable compoundhas a boiling point of from about C. to about 5 C.

References Cited by the Examiner UNITED STATES PATENTS 984,029 2/1911Scheuble 67-22 1,628,066 5/1927 Rose.

3,215,186 11/1965 Levitt l5863 ABRAHAM G. STONE, Primary Examiner.

R. E. BAGVVILL, Assistant Examiner.

1. A LIQUIFIED PETROLEUM GAS COMPOSITION CONSISTING ESSENTIALLY OFLIQUIFIED PETROLEUM GAS HAVING NOT MORE THAN FOUR CARBON ATOMS AS THEMAJOR INGREDIENT AND DISSOLVED THEREIN A READILY VAPORIZABLE COMPOUND OFA CHROMOPHORIC ELEMENT IN AN AMOUNT SUFFICIENT TO IMPART A VISIBLE COLORTO A FLAME OF SAID LIQUIFIED PETROLEUM GAS.